Various attempts have been made to provide a shoe sole construction that combines the look of leather with the durability and traction of rubber or other synthetic material. For example, in one such construction, a thermally moldable material is injected onto the entire top surface (i.e., shoe-side) of the leather sole, with a portion of the material extending into and through a cut-out region in the sole. However, this construction presents several disadvantages. First, the thermal material is visible at the sole edges between the midsole and the leather sole itself. Second, if the thermoplastic material is not evenly distributed, the heel of the shoe will not sit properly. Third, the construction is simply too heavy and too rigid, and delamination too often occurs at the shoe edges. Another construction utilizes a synthetic portion attached only on the street-side of the sole, but sole failure or separation has been a recurring problem in such a construction. Still another construction includes a thermoplastic insert molded into a cut-out region in the sole, but this construction has been unsatisfactory because the thermoplastic material has tended to shrink and to pull away from the edge of the cut-out region on the street-side of the sole, resulting in sole failure or separation.
It is therefore an object of the present invention to provide a sole construction comprised of leather and synthetic material in which the sole is lightweight and relatively flexible.
It is another object of this invention to provide such a sole construction having an aesthetically pleasing appearance with no thermal material visible at the edge of the sole.
It is a still further object of this invention to provide a sole construction in which the synthetic material is firmly secured to the leather so as to prevent its separation from the leather, particularly at the edge of the thermal insert, and in which the material does not shrink away from the sole.